Cutting the DFW notch?

[FatSebastian]

I am curious how others cut the notch / recess / inset into the body to accommodate the offset of the dominant front wheel (DFW).

In our racing heydays we pretty much just shaved off the entire body by ~1/16" from the front until just past the back of the wheel (here's a body so cut from Vitamin K). We did it this way because it was fast and easy to do on the available equipment (bandsaw with fence). For a more symmetrical front, I think we also tried using a Forstner bit to get a wheel-shaped recess into the block, although the point of the bit will wallow out the opening of the DFW axle hole a little.

But I have seen some precisely carved out wheel notches on some bodies. Some notches go the span of the wheel; others only notch out the wood at the hub and tread areas (so three small notches in a plank).

What techniques and tools are being leveraged to make precise (and cosmetically appealing) notches that don't just start shaving from the front of the car? Combed cut-outs? Sanding sticks? Chisels, files, or rasps? Router? For example, Doc Jobe used a hacksaw and a jeweler's screwdriver as a "chisel" to make his wheel notches.

[exoray]

For a more symmetrical front, I think we also tried using a Forstner bit to get a wheel-shaped recess into the block, although the point of the bit will wallow out the opening of the DFW axle hole a little.

I would not do it to a premium Forstner bit, but using a cheap import one the point on the Forstner bit is more a visual alignment indicator vs a functional needed part of the bit, thus it can be ground off/shaped into a flat cutter and blended to the bottom cutting blade profile next to it, and then using a clamping jig and a drill press you could get very nice round cut-outs to the virgin block of wood prior to any other shaping quite easily without any damage to the axle hole...

[Vitamin K]

Funnily enough, I have not felt the need to notch the front end since that build.

I think since then, we've started putting a lot more camber on our DFW axles, and I think that keeps the edge of the wheel further from the body.

[whodathunkit]

Hole plug cutter or end mill bit on a drill press
With fence. Back in the day!
Today scroll saw and sand paper is what I use.

[FatSebastian]

...we've started putting a lot more camber on our DFW axles, and I think that keeps the edge of the [trailing rear] wheel further from the body.

Ah. So, the more extreme positive camber of the DFW obviates the need to add a recess / cut-in behind the DFW. Makes sense, although TurboDerby's ebook (p. 37) still suggests a notch depth of 0.041" for 8 degrees ( does anyone cut wood precise to a thousand of an inch?)

That kind of observation partly motivates my question. We also run more positive camber than we used to (thanks in part to drill jigs that induce it), and lately we have not added any inset into the body to accommodate recessing the DFW either. The reason? Once we forgot about adding a notch until after the car was finished, and it didn't seem to create a significant performance penalty, so we forewent that step on later cars because the way we always did it was a bit inelegant. But then again, maybe we weren't racing at a performance level where the lack of notching mattered as much. (And after all, the typically recommended inset of ~1/16" is still pretty slight, if you think about it.)

Since we got out of the habit of notching, I wondered how folks were creating their notches. Tutorials that recommend adding a notch don't always suggest the technique for removing such a shallow amount.

[Vitamin K]

I feel like I'm getting a little bit confused between narrowing (or shaving) the DFW side of the car, and cutting a clearance notch to keep the wheel from potentially rubbing. While we haven't bothered with a clearance notch in quite some time, we do still sometimes narrow the front end of the car. I'm not sure whether narrowing is required when you have a lot of positive camber (because positive camber will move the edge of the wheel inwards on its own).

I still kind of tend to want to bring the DFW side in a 1/16", though I haven't really done extensive comparison testing to see if it makes much of a difference. I guess I just feel better about the car when we do.

[FatSebastian]

I still kind of tend to want to bring the DFW side in a 1/16", though I haven't really done extensive comparison testing to see if it makes much of a difference. I guess I just feel better about the car when we do.

The need, and depth, of an inset can be argued via geometrical consideration for maximizing the separation of both rear wheels from the rail given straight-line motion and an assumed rail width. One might argue that an inset may not be needed as long as the trailing rear wheel never touches the track, but that's probably left as a separate topic...

The intended question for this topic is: how does one cut this ~1/16" recess / notch / cut-in (whatever you want to call it) in a way that doesn't involve just shaving the side of the car starting at the front bumper?

[Hyperfocus]

I still kind of tend to want to bring the DFW side in a 1/16", though I haven't really done extensive comparison testing to see if it makes much of a difference. I guess I just feel better about the car when we do.

The need, and depth, of an inset can be argued via geometrical consideration for maximizing the separation of both rear wheels from the rail given straight-line motion and an assumed rail width. One might argue that an inset may not be needed as long as the trailing rear wheel never touches the track, but that's probably left as a separate topic...

The intended question for this topic is: how does one cut this ~1/16" recess / notch / cut-in (whatever you want to call it) in a way that doesn't involve just shaving the side of the car starting at the front bumper?

While I am certainly not experienced with this to provide a personal example, when I think of the intended question, I think "You'd need a notch for the wheel edge as it spins to ensure clearance, but also a notch for the hub to be closer to the center of the body". I imagine if you cut a 1/16" notch from the front of the car all they way to behind the DFW, You'd need to be very sure of a few things, such as ensuring the car body is perfectly straight and 90 degrees to the wall of the saw, then you'd also have to ensure the blade itself is precisely honed in with no horizontal or vertical tilt.

[Vitamin K]

I still kind of tend to want to bring the DFW side in a 1/16", though I haven't really done extensive comparison testing to see if it makes much of a difference. I guess I just feel better about the car when we do.

The need, and depth, of an inset can be argued via geometrical consideration for maximizing the separation of both rear wheels from the rail given straight-line motion and an assumed rail width. One might argue that an inset may not be needed as long as the trailing rear wheel never touches the track, but that's probably left as a separate topic...

The intended question for this topic is: how does one cut this ~1/16" recess / notch / cut-in (whatever you want to call it) in a way that doesn't involve just shaving the side of the car starting at the front bumper?

My little 1x30 HF belt sander makes it pretty easy to just inset the wheel area, as opposed to shaving the entire side.

[Vitamin K]

The need, and depth, of an inset can be argued via geometrical consideration for maximizing the separation of both rear wheels from the rail given straight-line motion and an assumed rail width. One might argue that an inset may not be needed as long as the trailing rear wheel never touches the track, but that's probably left as a separate topic...

The intended question for this topic is: how does one cut this ~1/16" recess / notch / cut-in (whatever you want to call it) in a way that doesn't involve just shaving the side of the car starting at the front bumper?

While I am certainly not experienced with this to provide a personal example, when I think of the intended question, I think "You'd need a notch for the wheel edge as it spins to ensure clearance, but also a notch for the hub to be closer to the center of the body". I imagine if you cut a 1/16" notch from the front of the car all they way to behind the DFW, You'd need to be very sure of a few things, such as ensuring the car body is perfectly straight and 90 degrees to the wall of the saw, then you'd also have to ensure the blade itself is precisely honed in with no horizontal or vertical tilt.

I wouldn't worry too much about it. I just eyeball it. After all, the angle of the wheel is controlled by the angle of the axle hole, which is already bored and unaffected by shaving the body.

Now, I do sometimes wonder if it might be worth attempting to angle the side of the body for the DFW to match the camber of the axle, but I've never really tried that.

[FatSebastian]

I think "You'd need a notch for the wheel edge as it spins to ensure clearance, but also a notch for the hub to be closer to the center of the body".

Yes, there are two generic approaches:

1. Notch out the DFW hub recess by ~1/16", and then make separate notches for tread clearances (so three notches)
2. "Shave" (recess) the entire area behind the DFW by ~1/16" (one wide notch)

VK's pic I linked actually showed a hybrid of these two; the body was shaved from the front and a "bonus" notch was made to help guarantee clearance for toe-in.

Usually the axle holes or axle slots are made while the true block and full-width; that is an initial, but separate, process. After the axle openings are positioned, the squareness of the block relative to the blade is probably not super critical for other cuts, including the removal of ~1/16" of material from behind a front wheel.

[FatSebastian]

My little 1x30 HF belt sander makes it pretty easy...

I don't have one of those myself, but I thought that this subject could be a good application for one. If only it was a 1.18+ x 30 belt sander!

[Vitamin K]

My little 1x30 HF belt sander makes it pretty easy...

I don't have one of those myself, but I thought that this subject could be a good application for one. If only it was a 1.18+ x 30 belt sander!

Hah. It is a good little tool. Good for basic shaping and also sharpening knives.

It's quite easy to just mark a pencil area that you want to recess and move the body slightly to make the cut against the belt.

Sent from my moto g(9) play using Tapatalk

[FatSebastian]

1. Notch out the DFW hub recess by ~1/16", and then make separate notches for tread clearances (so three notches)

Here is a stand-alone illustration of the three-notch approach courtesy of Doc Jobe:

https://twitpic.com/bze4ui

[Hyperfocus]

While I am certainly not experienced with this to provide a personal example, when I think of the intended question, I think "You'd need a notch for the wheel edge as it spins to ensure clearance, but also a notch for the hub to be closer to the center of the body". I imagine if you cut a 1/16" notch from the front of the car all they way to behind the DFW, You'd need to be very sure of a few things, such as ensuring the car body is perfectly straight and 90 degrees to the wall of the saw, then you'd also have to ensure the blade itself is precisely honed in with no horizontal or vertical tilt.

I wouldn't worry too much about it. I just eyeball it. After all, the angle of the wheel is controlled by the angle of the axle hole, which is already bored and unaffected by shaving the body.

Now, I do sometimes wonder if it might be worth attempting to angle the side of the body for the DFW to match the camber of the axle, but I've never really tried that.

Right, you'd have drilled the axle hole already. Ignore my comment haha. I was thinking of if you were drilling the axle holes after the cut.